I don't think all jurisdictions make that distinction to start with and even if they did and societies really wanted to go there: not sure why a licensing regime on generators with associated cryptographic information in the images could not work. We don't have to be broadly permissive, if at all.

I agree with you, but in some jurisdictions the distance between stuff generated with AI and actual photographs of child abuse are treated rather closely; either way, possessing either could result in what the England & Wales calls a "sexual harm prevention order" (SHPO). To me the idea that someone could be served such an order without ever possessing real CSEM (or "child porn"), never mind actually never being near a child is rather worrying.